The invention relates to a thermostat metal damper means for the flue of a gas-fired apparatus such as a home water heater and the like.
Gas-fired home appliances such as gas hot water heaters and furnaces have flues which vent gaseous combustion products from the appliances outside the home. In conventional appliances, thermally responsive dampers open the flue when gas firing occurs but close the vent when no gas firing is taking place. In that way, the damper provides the necessary venting but avoids heat loss from the hot water tank or the like through the flue and also avoids the entry of cold outside air into the home. In a typical gas vent damper, for example, vanes of thermostat metal are arranged to extend over the flue to block venting through the flue when the vane temperatures are below a selected level. However the vanes are positioned to be heated when gas combustion occurs for flexing to positions which open the flue vent. The vanes remain open as long as gas firing continues and automatically return to their original position closing the flue when the vanes cool after gas-firing is terminated.
In the typical gas vent damper as thus described, the thermostat metals which have been used have provided the desired temperature response over a long service life despite the corrosive gas flue environment to which the damper vanes have been exposed. However, the thermostat metals have been expensive, have employed metal alloys which are not widely available, and have incorporated substantial proportions of materials such as cobalt which are in relatively short supply. In the present energy crisis when it can be anticipated that such vent dampers for gas-fired appliances will find more widespread use and when the demand for such thermostat metals can be expected to substantially increase, it would be desirable to provide an improved vent damper and a thermostat metal for use in such a damper utilizing less expensive, more widely available metal alloys which do not incorporate large constituents of materials which are difficult or expensive to obtain.